Process of concentrating nitric acid.



.To all whom it may concern.-

HARRY PAULING, or ennsnnxmonnn, GERMANY, 'assIGNon T0. s'ALPETEnsAUnE- .INDusrnIE-eEsnLL'scHA r, e. m. B; 11., oFoELsENKmcHEn, GERMANY.

PROCESS or; qoNcEN'rnnrrNG NITRIC ncrn.

1,031,865. No l awin Be it known thatI, HARRY PAULING, 1nan ager, subject of the King of Saxony, resid- 'ous Nitric Acid and the Like with Acid and other Hygroscopic Substances and I do hereby declare the following to be ing at 84 Vvilhelmstrasse, Gels'enkirchen, IV., in the Kingdomof Prussia, German Empire, have invented anew and useful provement in Processes of -,Treat in gulfuric a full, clear, and exact description of the same;

This invention relates to processes of concentrating or otherwise treating aqueous acids; and it comprises a process wherein a current of steam or other suitable hot gas is introduced into an apparatus, such as a distilling column, near one end thereof, a hygroscopic dehydrating agent, .such as sulfuric acid or some other suitable hygroscopic substance, is introduced into the column at another point and travels in a direction opposed to that of the introduced-hot gas, and an aqueous 'acid, specificallydilute nitric acid, is led-into the common path of the 'counterflowing currents atv some intermediate point and joins the current'of .the

drying agent, vapors of strong nitric acid being evolved'and passing in the direction of the introduced hot gases beyond the point at which. the aqueous acid is led in, thus meeting the substantially pure drying agent in the latterpart of their course through the apparatus; all as more fully hereinafter set forth and as claimed;

In another and copendingapplication, Serial No. 584,123, filed September 27, 1910, I have described and claimed a; process wherein a mixture of aqueous nitricfacid with concentrated sulfuric acid, best substantially free of: impurities such as nitro-sulfuric acid, etc., is treated with a counter-flowing current of a hot gas, highly concentrated nitric acid being vaporized and condensed,

while relativelydilute sulfuric acid is obtained as a result of the dehydration of the nitric acid. I have found however that the result is improved by separately introducing 4 the drying'agent, for example sulfuric acid, before the aqueous acid which is'to be treat ed; that is-to say, when using a verticalcolumn the drying agent is introduced at the top, and the aqueous acid at a point farther down. By this means'the vapors generated.

by the heat are caused to come into contact Specification of Letters-Patent. Application filed epte nper 27,1910. fibrialllo. 584,124.

Patented July9, i912.

'- with pure hygroscopic 'matter. This enables a higher degree of concentration to be.

obtained, and effects a saving in the consumption'of hygroscopic matter.

It s convenient to carry out my improved process in a vertical distilling column or the like, provided with means for introducing a hot-gas at or near the base, means near the top for withdrawing vapors of concentrated nitric acid, and means at some intermediate point for introducing aqueous acid which is to flow downwardly in the column against the current of hot gas introduced below. At a point somewhat above that at which the aqueous acid enters, there should be an inlet through which the hygroscopic agent detrimental to nitric acidmay be used in stead of stean1 ,but steam is most advantageous. The sulfuric acid abstracts much water from the dilute nitric-acid immediately upon mixing therewith, but its avidity for water is enhanced by the heating eii'ect of the gas current flowing against the acid mixture, and, the dehydration of the nitric acid is thus rendered much more complete.

Where steam is used, its latent heat is thus utilized to great advantage. As a result of this treatmentthe nitric acid is vaporized, and the concentrated vapors pass upwardly through thecolumn beyond the point Where aqueous nitric acid is" admitted, meeting thereabove the current of substantially pure sulfuric acid where the dehydration is ren- 1 dered substantially complete. The vapors of nitric acidleaving the top of the apparatus are of very high'concentration and are condensed in' any convenient manner. The spent sulfuric acid leaving the base of the. column contains. practically all the water originally'in the dilute nitric acid, while it is itself, substantially free of nitric acid. What I claim is f '1. The process of concentrating aqueous acid, which comprises establishing a current of a hygroscopic dehydrating agent and .a counterflowing current of a hot gaseous medium eomprislng steam traveling in a common path, and introducing at an intermediate point in the common path of the opposed currentsa current of an aqueous acid traveling in the same direction as said current of dehydrating agent.

2. The process of concentrating aqueous nitric acid, which comprises establishing a current of substantially pure sulfuric acid and a counterflowing current of steam trav-.

cling. in a common path, introducing into said common path of the opposed currents a current of aqueous nitric acid traveling in the same directlon as sald current of sulfuric acid, and withdrawing vapors of highly concentrated nitric acid at a point prior to that at which said sulfuric acid current comes in contact with aqueous nitric acid. r

3. Theprocess of concentrating aqueous nitric acid, whichcomprises passing steam into the base of a column, introducing substantially pure sulfuric acid into said column near its top,-introducing aqueous nitric acid into said column at some intermediate point below that at which sulfuric acid is admitted, and withdrawing vapors of concentrated nitric acid from the column at a point above thatat which aqueous nitric acid is admitted, whereby the nltric acid vapors evolved-in the lower part of the column pass for some distance in contact with substantially pure sulfuric acid.

In testimony whereof, I have signed my name-to this specification in the presence of two subscribing witnesses.

. HARRY PAULING.

Witnesses MATHiLDE K. HELD, A. V. W. Corrun. 

